Consider the diagram of a molecular beam apparatus provided in the text.

In the design of the apparatus, it is important to ensure that the molecular beam effusing from the oven does not collide with other particles until the beam is well past the skimmer, a device that selects molecules that are traveling in the appropriate direction, resulting in the creation of a molecular beam. The skimmer is located 10 cm in front of the oven so that a mean free path of 20. cm will ensure that the molecules are well past the skimmer before a collision can occur. If the molecular beam consists of O₂ at a temperature of 500. K, what must the pressure outside the oven be to ensure this mean free path?

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RT 1 = 0.20 m = m? (see Table 33.1) 4.0 x 10-19 бо, PN/20 PNA